1. Field of the Invention
The present invention relates to a stilbene derivative, a light emitting element using the stilbene derivative, and a light emitting device and an electronic appliance having the stilbene derivative or the light emitting element.
2. Description of the Related Art
A light emitting element which has characteristics such as thinness, lightweight, and rapid response is expected to be applied to flat panel displays of the next generation. In addition, it is said that a light emitting device in which light emitting elements are arranged in matrix is superior to a conventional liquid crystal display device, especially in wide viewing angle and visibility.
A light emitting element has a structure in which a layer including a light emitting substance is interposed between a pair of electrodes (an anode and a cathode). It is said that, in such a light emitting element, when voltage is applied between the electrodes, holes injected from the anode and electrons injected from the cathode are recombined in the layer including a light emitting substance, so that molecular excitons of the light emitting substance are formed, and light is emitted when the molecular excitons return to the ground state.
Accordingly, emission wavelength of a light emitting element is determined by a band gap of a light emitting substance contained in the light emitting element. Therefore, various emission colors can be obtained by devising a structure of the light emitting substance. A full-color light emitting device can be realized, by forming light emitting elements capable of emitting red light, blue light, and green light, which are the three primary colors of light, and using the light emitting elements.
However, there has been a problem such that it is difficult to realize a light emitting element having high reliability and excellent color purity. As a result of recent development of materials, high reliability and excellent color purity of light emitting elements of green and red have been achieved. On the other hand, excellent color purity and high reliability of a light emitting element of blue has not been sufficiently realized, and many researches thereof are carried out (for example, Reference 1: Japanese Published Patent Application No. 2004-75580).